Rob and I and climategate held an impromptu live support session today using DimDim and it went pretty well. We had a chance to play with some of the features and were able to help a new user understand a couple of concepts better.
Audio was a bit of a problem, but not impossible. I think it's important that participants use headphones if possible to minimize the echo effect of desktop speaker.
Thanks for joining in, Rob! It was a pleasure to talk to you.